A whipstock is a tool inserted in the wellbore to deflect a mill, drill bit or other tools in a direction that is angularly offset from the orientation of the original wellbore. The face of the whipstock is thus oriented at a selected directional azimuth relative to the borehole axis. One type of whipstock is disclosed in U.S. Pat. No. 4,285,399.
At various times, oil well operators are desirous of specialty whipstock assemblies which achieve particular purposes. U.S. Pat. Nos. 5,398,754 and 5,595,247 disclose retrievable whipstock assemblies. U.S. Pat. No. 5,566,762 discloses a through tubing whipstock assembly. A whipstock assembly with a spring biased reference sleeve is disclosed in U.S. Pat. No. 6,488,295.
The prior art provides reliable whipstock assemblies for many applications, but commonly accepted whipstock assemblies, and particularly whipstock anchors, are complex with numerous moving parts. Other whipstock assemblies are comparatively simple, but tend to break loose from the casing string when high forces are transmitted to the whipstock assembly. Still other whipstock assemblies have a significantly reduced diameter bore through the whipstock anchor. When the whipstock is retrieved from the set anchor, tools cannot be reliably passed through the anchor due to the restricted diameter bore.
The disadvantages of the prior art are overcome by the present invention, and an improved whipstock anchor assembly is hereinafter disclosed.